Jennifer Lawrence doesn’t merely use a mop in her latest David O. Russell collaboration, Joy. She plays the inventor of the first self-wringing mop, and uses her creation so effectively and persuasively that she is able to convince a Home Shopping Network executive (played by Bradley Cooper) to order 50,000 of the product and later sell millions after demonstrating her tool on the network. Needless to say, it was important that Lawrence understood the art of mopping when it came time to film the drama—but, as the Oscar-winning actress explains in a new interview, she fell a bit short.

During a conversation with NPR’s Terry Gross that aired on Monday, Lawrence explained that she practiced mopping before it came time to film. “There was a mop [in] my trailer,” the actress said of her practical preparation. “And so I would practice it, you know, practice, like, technique and then—and just kind of getting used to it. And there were so many Miracle Mops on set and I would start working them and, like, really just trying to study it.

“But when I first showed Bradley Cooper in the showroom the mop,” Lawrence said, speaking of the scene in which her character tries to pitch her product to the H.S.N. exec, “he watched me and he was like, ‘No, no, no, Jen, that’s not how you mop.’ And he showed me how to properly mop.”

If anyone needs a mopping tutorial, Bradley Cooper is apparently the person equipped for the job. As Lawrence explained, her co-star was actually more prepared for Joy’s titular role than she was, in part because his mother sent him off to college with an actual Miracle Mop.

“His mom watched QVC every day,” Lawrence explained. “They always had QVC boxes in the house. I mean, he knew all about that world and I knew nothing. And I had an O.C.D. mom, so she would always give us a bunch of chores and tell us what to do, but she couldn’t actually live with it being done the wrong way, so it never actually mattered. She would always end up doing it.”

Last week on a red carpet, Cooper admitted, somewhat abashedly, that he is indeed a mop expert.

“The Miracle Mop I actually took to college,” the actor told E! “It was very embarrassing. But yeah, mopping was part of the chores that I got. My sister was allocated other things but I was vacuuming and mopping the house.”

In fact, Cooper added that his mother, Gloria, is such a fan of home shopping that, “She actually was a consultant for David on the movie when he was conceiving it because she’s a huge disciple of QVC.”

Take a look at Lawrence showing off her new skill, in a scene from Joy, below.